The invention relates to a control system for supplying a gas flow to a gas consumption apparatus, comprising a gas supply pipe which can be connected to the apparatus and which has an electrically controlled gas control valve, and an electronic control unit. Such a control system is disclosed in EP-A-0 077 286.
In a first embodiment of this known system, use is made of an electronic control regulation which adjusts the control valve on the basis of a signal representing the desired gas flow, and of a flow-rate or throughput sensor whose output signal is fed back as a correction to the electronic control system, which then readjusts the control valve. Apart from the fact that such throughput sensors are inaccurate and unreliable, this system is much too slow if fast response times are desired. In a second embodiment of this known system, use is made of a simple valve-positioning loop which operates the motor of the control valve on the basis of a composite input signal. The composite input signal essentially comprises a combination of inlet gas pressure and rotary speed of a gas engine. Corrections can be made thereto by means of a few less important variables, such as atmospheric pressure, air temperature and gas temperature. This last embodiment is less cumbersome and also operates more rapidly than the first embodiment but is insufficiently accurate. The object of the invention is therefore to eliminate the abovementioned problems.
Furthermore, in an application of such control systems, namely in gas injection systems fop gas combustion engines, the homogeneity of the gas/air mixture in the cylinders is of great importance in achieving as low as possible an emission of harmful substances. A requirement related thereto is a very accurate gas metering with rapid response to alterations in load and rotary speed. In practice, it is of exceptional importance to regulate the gas/air ratio extremely accurately in accordance with any desired curve during alteration from starting rotary speed to full load at maximum rotary speed. This should also be achieved with varying gas inlet pressures and temperatures. The known systems do not meet these requirements. The object of the invention is also to fulfill the latter.